Conventionally, a plurality of methods or apparatuses have been disclosed for the purpose of manufacturing a foam gasket, etc. foamed by mixing gas into a pressurized high-viscosity material, and subsequently applying it under an atmospheric environment. For example, in Japanese Patent Laid-Open No. H10-272344, a method for mixing gas into a high-viscosity material has been disclosed in which using a piston pump in which a piston reciprocates in a cylinder to perform a suction stroke and a discharge stroke, the gas is supplied in the cylinder in the suction stroke of the piston pump, the piston reaches a suction end, the suction stroke ends, and an inside of the cylinder becomes a state of being filled with the gas having an adjusted pressure, and subsequently, the high-viscosity material is supplied in the cylinder, the discharge stroke of the piston pump is performed after end of the supply of the high-viscosity material, and in which the gas and the high-viscosity material are discharged to a conduit in the discharge stroke.
In addition, in Japanese Patent Laid-Open No. H09-94450, there has been disclosed a method for mixing gas into a fluid material having the steps of: alternately sending out the fluid material and the gas through the same path by a comparatively low pressure of approximately 1 to 5 kg/cm2; and pressurizing the fluid material and the gas to a high pressure of approximately 100 to 400 kg/cm2 by a high-pressure pump in the middle of the path.